Stabilizing wool against shrinkage



Patented May 6, 1952 STABILIZING WOOL AGAINST .SHKINKAGE Stockman C. Peckham, deceased, late. of Wilmington, Del., by Gladys W. Hill, executrix', Wilmington, Del., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August2, 1949, Serial No. 108,236

7 Claims.

This invention relates to highly useful products comprising wool and polyacrylonitrile fibers and in particular to woolen materials which are stable to shrinkage.

The problem of wool shrinkage has been considered by fiber experts for many years. Several theories for the felting phenomenon and shrinking of wool has been suggested but none of these theories are as yet widely accepted. Recent publications indicate that this problem and means for preventing the shrinkage of wool are receiving increasingly active attention.

It is recognized that wool and other natural hair fibers have a' rough scaly surface, these scales being aligned inone direction along-the fiber axis. The felting shrinkage of wool can be reduced toinsignificance by at least partial obliteration of the scales. Thus, the surface of wool fibers can be changed by acid or alkali treatments which result in the attendant diminution of shrinkage in articles prepared from these woolen fibers. However, such drastic treatments also affect some of the desirable properties of wool and render it unsuitable for use in its normally broad line of applications.

A second and more widely used chemical treatment for shrinkproofing wool comprises resin impregnation. By this process, woolen articles are impregnated with a resinous material, such as a condensation product of melamine and formaldehyde, which theoretically fills up the scales on the wool fiber and thereby forms a smooth surface. A modification of this procedure comprises impregnating the wool fibers with a vinyl-type monomer and a polymerization catalyst and thereafter heating the material to form a polymer in situ. These treatments, however, tend to change the drape and hang of the woolen goods.

Treatment of wool fibers with chlorine is also a popular method for reducing the felting characteristics of wool. However, the chlorinated wool suffers in the loss of tensile strength and abrasion resistance.

The dilution of wool with other fibers, both natural and synthetic, in an effort to reduce shrinkage has been tried. In every case, however, it was found that shrinkage could not be eliminated unless the mixture contained less than 50% wool, or, in other words, over 50% of the diluent.

It is an object of this invention to prepare a predominately woolenyarn which will not shrink upon washing by ordinary procedures. It is a further object ofv this invention to prepare a non-shrinkable, woolenyarn which retains the other desirable properties of wool. Other objects will become apparent hereinafter.

The. objects of this invention are accomplished by blending with wool as little as 15% of a staple Continuous filament polyacrylonitrile yarn, ISO-denier, prepared bydry-spinning a 20% solution of, the polymer in dimethyl formamide, was combined into a 2,250-denier ropewhich was then drawnsix times its length in an atmospheric steam-drawing chamber. Staple chips were cut from this material and boiled for approximately 15 minutes in water. This boiling treatment removed the residual solvent in the yarn and crinkled the fibers. A lubricating and antistatic yarn finish was applied to the staple, after which the fibers were dried. This polyacrylonitrile fiber staple was 1.5-denier per filamentand 1.5" in length. Sliver of the polyacrylonitrile staple was combined with 2" grade 64s wool top, on the drawing frame of the American (modified cotton) system of spinning. The American system is described on pages 37 to 43 of the Papers of the American Association of Textile Technologists for the period November, 1946to February, 1947. By this means the following samples ofJyarn were prepared:

Table I Percent Pen PO13 cent Wo sted Cotton TWISF Calculated 10 an] Wool Count Count f Turns/In.

liltgllfi Top plur i or 30 l/Sfi 24/1- 3. 2 15. 7 30 70 1136 24/1. 3. l5. 7 15 1136 24/1 3. (3 l7. 6 i5 85 l/3G 24/1 3. 2 l5. 7 O I/36 24/1 3. G 17. 6 0 100 l/36 24/1 3. 2 l5. 7

These yarns were knitted into socks on an English Komet knitting machine that knits two. ends together using a single-feed. It was a'200-needle machine with a 3.5 diameter cylinder having; approximately 18 needles to the inch. Although size 11 socks were made from the yarn, they were actually made a half size larger in the greige than 11, as is customary in socks of this kindto allow for shrinkagein dyeing and finishing. After knitting, the socks were looped and mended using; the thread normally employed to loop' and mend nylon/wool blend socks. The socks were then dyed with Neutral Yellow GS for hour in a boiling aqueous bath containing ammonium sulfate. After dyeing, the socks were boarded and tested for shrinkage essentially according to Federal Specification CCC-T-191A.

The test was carried out in the following manner: The socks were relaxed by wetting out in an aqueous bath at 80 F. containing 1% of Peregal, a polyether alcohol wetting agent manufactured by General Dyestuffs Corporation, for 20 minutes. The socks were dried on a horizontal wire screen without stretching. This procedure is necessary to eliminate the errors in shrinkage determination due to over or under boarding. The length of the socks was then measured on a Schiefer machine. This device is illustrated and described in the Federal standard stock catalogue, section 4, part 5, under CCC-T-191A. The socks were then laundered in a Smith rotating drum machine for 2 hours at 140 F. The bath contained 100 grams of olate flake (a very low titer, neutral flake soap), 20 grams of soda ash (to promote felting) and 15 grams of sodium hexametaphosphate (water softener). The socks were then given two 5- minute rinses in water at 140 F. After drying on a screen in a non-stretched condition, they were again measured on the Schiefer machine. Four additional 2-hour launderings were made in the same manner as described above. The results of these tests are given in Table II as average shrinkage in per cent:

Table II Average Per Cent Shrinkage 4 then tested one time for residual shrinkage by the method described in Federal specification CCC-T191A. Table III contains the results of these tests:

A 24% solution of 95/5 acrylonitrile/Z-vinyl pyridine copolymer in dimethyl formamide was dry spun and drawn 4.25 its length in an atmospheric steam chamber. The drawn fibers, in the form of a 38,000 denier tow, were passed into a mechanical crimper, imparting 10-12 crimps per inch, cut into staple chips, a lubricating antistatic yarn finish applied, and the staple chips finally dried. This fiber staple was 3 d. p. f. and 2.5" in length.

A portion of this staple was spun on the American (modified cotton) system of spinning to 2/20 w. c. yarn, having 9 t. p. i. twist in the singles and 3.9 t. p. i. in the ply.

The remaining portion of the above 95/5 acrylonitrile/2-vinyl pyridine copolymer staple Item G of this table comprised socks prepared from nylon and 65% grade 64s wool top as described above. The shrinkage results for the nylon/wool blend socks are entered here for comparative purposes.

In socks of the size tested, 1% shrinkage means that the socks have lost slightly over in the length of the foot. Since the test is hardly that accurate, anything less than 1% shrinkage or elongation should be disregarded. Shrinkages of l-2% in socks are not considered excessive and could probably not be detected by a wearer. The progressive type shrinkages shown in items E, F and G of Table II are excessive and undesirable.

EXAMPLE II This example is designed to show that the finishing treatment given the socks has little or no effect on the shrinkage unless a special shrinkproofing treatment is used. Socks for this test were prepared in the manner described in Example I from two yarn samples, one containing 65% wool and 35% polyacrylonitrile staple and the other containing 65% wool and 35% nylon staple. Some of each of these socks were preboarded and some were not preboarded during finishing. In addition, some of the nylon/wool socks were preboarded and given a shrinkproofing treatment. These socks were Table IV Fl er Clent m. Per Cent Worsted TPI TPI smmlc 2 5 3 2 Wool Top Count Singles Ply Fiber These yarns were knitted into 6x3 rib construction socks on an English 132 needle K'omet knitting machine that knits two ends together using a single feed. Although size 11 socks were made from the yarn, they were actually made a 0.20% Nyaciza neutral silk yellow GX 2.5% Althouse silk brown RG 0.44% Jos. S. Vila neutral Czanine 3B for two hours in an aqueous bath containing 30% Glaubers salt at a temperature of approximately 205 F. After dyeing, th socks were boarded and tested for shinkage essentially according to Federal specification CCC-T-19l-A (described under Example I).

Tests for resistance to abrasive wear at the toe cap were made by mounting the samples over a metal surface and causing them to oscillate mechanically back and forth in contact with a wearing surface of special hosiery abrasive fabric held under an initial tension of nine pounds. In Table V are listed the number of single strokes necessary to wear holes in the toe caps of the various socks.

As shown above, as little as of acrylonitrile polymer staple in wool is effective. Amounts appreciably less than 15% will not work and amounts appreciably greater than 40% are unnecessary. Amounts ranging from 15% to 30% of the acrylonitrile homopolymer ar preferred and with copolymers amounts from 30% to 40% are preferred.

Further, copolymers of acrylonitrile may be used providing they contain at least 85% of acrylonitrile and up to 15% of copolymerizable monomers such as vinyl acetate, vinyl chloride, acrylic and methacrylic acids or derivatives and homologues thereof, styrene, methyl vinyl ketone, vinyl pyridines such as 2-vinyl, 4-vinyl, 5-ethyl- 2-vinyl, or 2-methyl5-viny1 pyridine and isobutylene or other similar polymerizable hydrocarbons. The polymers of acrylonitrile employed possess an average molecular weight of from 25,000 to 750,000 or even higher and preferably between 40,000 to 250,000 as calculated from the Staudinger equation. Of th various polymers polyacrylonitrile and acrylonitrile/vinyl pyridine copolymers are preferred. In order to get the desired stability against shrinkage, the wool/acrylonitrile polymer blends must be made as described above, that is, with staple. Blending of continuous filament polyacrylonitriles with wool is ineffective. This and the fact that so little of the acrylonitril polymer yarns are effective as compared to previously used diluents are indeed surprising.

The socks prepared from blends of wool with polyacrylonitrile staple fibers and used in the above-described tests possessed a good hand and drape and were warm to the touch. In addition. they possessed the desirable physical properties of wool. It can be readily seen from the examples that this invention provides a perdominately wool yarn retaining its wool-like properties, which is dimensionally stable to shrinkage normally at tendant to washing. In fact, yarns and fabrics comprising wool and as little as 15% polyacrylonitrile staple yarn do not shrink when given rather strenuous laundering treatments, and no special care is needed when washing these articles. In contrast to chlorinated wool, the yarns and fabrics of this invention possess an increased resistance to abrasion. This entirely new and un' expected phenomenon has boundless utility and represents a notable advance of extreme importance to the apparel field.

Any departure from the procedure described herein which conforms to the principles of the invention is intended to be included within the scope of the claims below.

What is claimed is:

1. A blend of fibers comprising wool fibers and from 15% to 40% by weight of said blend of staple fibers prepared from an acrylonitrile polymer containing at least acrylonitrile.

2. A blend of fibers comprising wool fibers and from 15 to 30% by weight of said blend of staple fibers prepared from polyacrylonitrile.

3. A blend of fibers comprising wool fibers and from 15% to 30% by weight of said blend of staple fibers prepared from polyacrylonitrile having a molecular weight from 40,000 to 250,000.

4. A blend of fibers comprising wool fibers and from 30 to 40% by weight of said blend of staple fibers prepared from a copolymer containing at least 85% acrylonitrile and up to 15% 2-vinyl pyridine.

5. A blend of fibers comprising wool fibers and from 30% to 40% by weight of said blend of staple fibers prepared from a copolymer containing acrylonitrile and 5% 2-vinyl pyridine.

6. A blend of fibers in accordance with claim 5 in which said copolymer has a molecular weight of from 40,000 to 250,000.

'7. A process for producing a woolen yarn of low shrinkage which comprises blending wool fibers with from 15% to 40% by weight based on the resultant blend of staple fibers prepared from an acrylonitrile polymer containing at least 8.5% acrylonitrile and converting the resultant blend of fibers into a yarn.

GLADYS W. HILL,

Ewecutrizc of the Estate of Stoclcrhan C. Peckham,

Deceased.

REFERENCES CITED The following references are of record in the I file of this patent:

UNITED STATES PATENTS 

1. A BLEND OF FIBERS COMPRISING WOOL FIBERS AND FROM 15% TO 40% BY WEIGHT OF SAID BLEND OF STAPLE FIBERS PREPARED FROM AN ACRYLONITRILE POLYMER CONTAINING AT LEAST 85% ACRYLONITRILE. 